WASHINGTON (Reuters) - The number of people banned from flying under the U.S. government's terrorism watch list has more than doubled over the last year, a counterterrorism source said on Thursday.
The list banning people from flight to the United States, or within it, has risen to about 21,000 names from about 10,000, said the source, who spoke on condition of anonymity to discuss security matters.
The increase is largely due to the failed Christmas Day 2009 bombing of a Northwest Airlines airliner headed for Detroit. The attempt resulted in a government examination of the list and a widening of those who could be put on it, the source said.
"Certainly, the review after Christmas Day was one of the big factors," said the source.
A review of files led to putting people on the list who would be a threat to U.S. security, not just to aviation. An individual was also added if there was proof the person had attended a guerrilla training camp, the source said.
The no-fly list is produced by the Federal Bureau of Investigation's Terrorist Screening Center. The aviation list is a subset of a larger list of suspected extremists.
The United States also is working with "foreign partners" to compile names, the source said, adding: "It's really a combination of factors."
A spokesman for the Transportation Security Administration declined to comment.
The increase has come even as the administration of President Barack Obama has said it is closer to defeating al Qaeda extremists than ever and has killed many of the network's senior figures.
(Reporting By Ian Simpson; Editing by Paul Thomasch)